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Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The focus of the grant was the use of Application Visualization System (AVS), developed by Advanced Visual Systems, Inc., for animating supersonic turbulent flows computed using Large Eddy Simulation (LES) . Three flow configurations are visualized: a turbulent flat plate supersonic boundary layer, an 8 deg supersonic compression corner and a 25 deg supersonic compression corner. The animations display the quantitative and qualitative features of the turbulence production and the complex physics of the shock wave turbulent boundary layer interaction.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The focus of the grant was the use of Application Visualization System (AVS), developed by Advanced Visual Systems, Inc., for animating supersonic turbulent flows computed using Large Eddy Simulation (LES) . Three flow configurations are visualized: a turbulent flat plate supersonic boundary layer, an 8 deg supersonic compression corner and a 25 deg supersonic compression corner. The animations display the quantitative and qualitative features of the turbulence production and the complex physics of the shock wave turbulent boundary layer interaction.
Author: Publisher: ISBN: Category : Languages : en Pages : 40
Book Description
An unstructured grid Large Eddy Simulation (LES) methodology has been developed for compressible high speed flows. The filtered compressible Navier-Stokes equations are solved on an unstructured grid of tetrahedra. The inviscid fluxes are obtained from an exact locally one-dimensional Riemann solver using Godunov's method. The viscous fluxes are obtained using a discrete analog of Gauss' Theorem. The reconstruction is performed using a Least Squares technique. The temporal integration is a Runge-Kutta method. The algorithm is overall second order accurate in space and time. Four flow fields have been computed: supersonic flat plate boundary layer, supersonic compression corner, supersonic expansion-compression corner and subsonic square jet. The computed results show close agreement with experiment and Direct Numerical Simulation, and validate the unstructured grid LES methodology.
Author: Peter R. Voke Publisher: Springer Science & Business Media ISBN: 940111000X Category : Technology & Engineering Languages : en Pages : 438
Book Description
It is a truism that turbulence is an unsolved problem, whether in scientific, engin eering or geophysical terms. It is strange that this remains largely the case even though we now know how to solve directly, with the help of sufficiently large and powerful computers, accurate approximations to the equations that govern tur bulent flows. The problem lies not with our numerical approximations but with the size of the computational task and the complexity of the solutions we gen erate, which match the complexity of real turbulence precisely in so far as the computations mimic the real flows. The fact that we can now solve some turbu lence in this limited sense is nevertheless an enormous step towards the goal of full understanding. Direct and large-eddy simulations are these numerical solutions of turbulence. They reproduce with remarkable fidelity the statistical, structural and dynamical properties of physical turbulent and transitional flows, though since the simula tions are necessarily time-dependent and three-dimensional they demand the most advanced computer resources at our disposal. The numerical techniques vary from accurate spectral methods and high-order finite differences to simple finite-volume algorithms derived on the principle of embedding fundamental conservation prop erties in the numerical operations. Genuine direct simulations resolve all the fluid motions fully, and require the highest practical accuracy in their numerical and temporal discretisation. Such simulations have the virtue of great fidelity when carried out carefully, and repre sent a most powerful tool for investigating the processes of transition to turbulence.
Author: M. Lesieur Publisher: Cambridge University Press ISBN: 9780521781244 Category : Mathematics Languages : en Pages : 240
Book Description
Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.
Author: Boris Galperin Publisher: Cambridge University Press ISBN: 0521430097 Category : Technology & Engineering Languages : en Pages : 626
Book Description
Originally published in 1993, this book was the first to offer a comprehensive review of large eddy simulations (LES) - the history, state of the art, and promising directions for research. Among topics covered are fundamentals of LES; LES of incompressible, compressible, and reacting flows; LES of atmospheric, oceanic, and environmental flows; and LES and massivelt parallel computing. The book grew out of an international workshop that, for the first time, brought together leading researchers in engineering and geophysics to discuss developments and applications of LES models in their respective fields. It will be of value to anyone with an interest in turbulence modelling.
Author: Chaoqun Liu Publisher: Bentham Science Publishers ISBN: 1681085976 Category : Technology & Engineering Languages : en Pages : 321
Book Description
This volume presents an implicitly implemented large eddy simulation (ILES) by using the fifth order bandwidth-optimized WENO scheme. The chosen method is applied to make comprehensive studies on ramp flows with and without control at Mach 2.5 and Re=5760. Flow control in the form of microramp vortex generators (MVG) is applied. The results show that a MVG can distinctly reduce the separation zone at the ramp corner and lower the boundary layer shape factor under simulated conditions. A series of new findings about the MVG-ramp flow are obtained, including structures relevant to surface pressure, three-dimensional structures of the re-compression shock waves, a complete surface separation pattern, momentum deficit and a new secondary vortex system. A new mechanism of shock-boundary layer interaction control by MVG associated with a series of vortex rings is also presented. Vortex rings strongly interact with air flow and play an important role in the separation zone reduction. Additionally, readers will learn about the governing equation, boundary condition, high quality grid generation, high order shock capturing scheme and DNS inflow condition in detail. This volume will, therefore, serve as a useful reference for aerospace researchers using LES methods to study shock boundary layer interaction and supersonic flow control.
Author: Jean-Pierre Chollet Publisher: Springer Science & Business Media ISBN: 9401156247 Category : Science Languages : en Pages : 436
Book Description
Progress in the numerical simulation of turbulence has been rapid in the 1990s. New techniques both for the numerical approximation of the Navier-Stokes equations and for the subgrid-scale models used in large-eddy simulation have emerged and are being widely applied for both fundamental and applied engineering studies, along with novel ideas for the performance and use of simulation for compressible, chemically reacting and transitional flows. This collection of papers from the second ERCOFTAC Workshop on Direct and Large-Eddy Simulation, held in Grenoble in September 1996, presents the key research being undertaken in Europe and Japan on these topics. Describing in detail the ambitious use of DNS for fundamental studies and of LES for complex flows of potential and actual engineering importance, this volume will be of interest to all researchers active in the area.
Author: NA Schumann Publisher: Springer Science & Business Media ISBN: 3663001970 Category : Technology & Engineering Languages : en Pages : 350
Book Description
This volume contains papers presented to a EUROMECH-Colloquium held in Munich, September 30 to October 2, 1985. The Colloquium is number 199 in a series of colloquia inaugurated by the European Mechanics Committee. The meeting was jointly organized by the 'Lehrstuhl fur Stromungsmechanik' at the 'Technische Universitat Munchen' and the 'Institut fur Physik der Atmosphare' of the 'Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt' (DFVLR) in Oberpfaffenhofen. 'Direct' and 'large eddy simulation' are terms which denote two closely con nected methods of turbulence research. In a 'direct simulation' (DS), turbu lent motion is simulated by numerically integrating the Navier-Stokes equations in three-dimensional space and as a function of time. Besides ini tial and boundary conditions no physical simplifications are involved. Com puter resources limit the resolution in time and space, though simulations with an order of one million discrete points in space are feasible. The simu lated flow fields can be considered as true realizations of turbulent flow fields and analysed to answer questions on the basic behaviour of turbulence. Direct simulations are valid as long as all the excited scales remain within the band of resolved scales. This means that viscosity must be strong enough to damp out the not resolved scales or the simulation is restricted to a lim ited integration-time interval only. In summary, DS provides a tool to investigate turbulent motions from first principles at least for a finite band of scales.
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Author: Peter R. Voke
Author: Sinisa Krajnovic
Author: M. Lesieur
Author: Boris Galperin
Author: Chaoqun Liu
Author: Siniša Krajnović
Author: Jean-Pierre Chollet
Author: NA Schumann